Have you hooked up any aftermarket equipment lately that runs directly off of a hot? Do you have any aftermarket equipment at all/ What kind of gauge do you have inside for the battery? Does the gauge show a charge or a draw on the battery while you are driving? Do you have anything like a cell charger plugged into the cigarette lighter? What are your driving habits? Do you drive only at night for only a couple of miles or do you drive in the daytime? I ran across this awhile back. It is a good way to test for a bad battery:

How to find the cause for an slow draining battery

Many Land Rovers are plagued by the 'flat battery' syndrome, especially the newer ones. After some days of not being driven the battery is dead flat. Under normal everyday driving those sympthoms do not appear.

The problem is in most cases a slow drain somewhere. It does not take that much to empty even a large battery over 3 or 4 days. An simple underhood or interior light is more than enough. But how to find it?

First make sure your battery is ok and fully loaden. Even a new battery is sometimes faulty. Drive to your local parts store and have them check your battery with an load tester.

If this is ok make sure your electronics don't mind being disconnected. Ask your dealer or have a look in your owners manual. Elder petrol engines (except new shape RRs) and all diesels except the TD5 are no problem.

Disconnect the positive clamp on your battery but take care not to touch the body metal with the wrench when doing this.

Now connect an small light between the + terminal and the clamp. Put the clamp on a rag so it can't touch the sheet metal. If any drain is present the light will glow. Or you can check the amount of drain with an small ammeter. An drain of 1-2 Watts can be tolerated. Next pull the fuse for the mechanic clock and the radio. Still any current flowing (light on)?

Ok, so you really have a problem. Now start pulling the fuses in the fuse box one by one until the light goes off. This is the circuit in which the problem lies. Check your manual or the indications in the cover of the fuse box to see which systems are connected to that fuse.

The next steps depend on the systems concerned. Try disconnecting each one of the parts connected in the circuit. Again it's the same - when the light goes out you've found the problem.

Even better than a light bulb is an buzzer. Many people have one of those annoying little rascals lying around. Use it.

In very new vehicles there are so many electric and electronic gadgets that problems are very common. Especially the immobiliser / alarm is known to be a can of worms. Those have best been left to an qualified auto electrician

Then there is this:

Battery complications:
don't let it put put a drain on you

Almost everyone who drives knows the frustration of a failed vehicle battery. No matter when a battery fails to start a car, it never seems to be at a convenient time or place, and the complications of finding and installing a replacement battery can seem endless.

Knowing what to expect from a vehicle battery – and what can be done to prevent inconvenient battery failure – are the keys to avoiding this common and stressful event.

Despite warranties that claim an expected battery life of four, five or six years, most vehicle batteries will fail after three and a half years, or even sooner, said Jeff Withrow, manager, Approved Auto Repair at AAA Colorado. The constant chemical reaction inside a lead-acid battery, vibration caused by driving and extreme changes in temperature all conspire to rob a battery of its ability to be recharge.

Car owners often assume their vehicle battery will be fine after a jump-start, only to experience a second battery failure the next time they try to re-start the vehicle. Car batteries are seldom tested as part of a regular vehicle inspection and maintenance routine, and many owners assume their vehicle battery will last much longer than it actually will.

"To end this frustration motorists will need to change their thinking about batteries," said Withrow. "New technology has made it possible to reliably determine the condition of a vehicle battery in a few minutes without removing the battery from the vehicle. This test should be requested by vehicle owners anytime they have their vehicle inspected."

The major functions of the battery are to supply current to the starter motor that starts the engine, provide power to electrical components and accessories when the vehicle’s engine is not running and to supply current when the electrical system load exceeds charging system capability. The battery also acts as a voltage stabilizer.

Before replacing a battery, have the battery, electrical and vehicle-charging system checked for problems. Signs of a weak battery are slow engine cranking, dim headlights and illumination of the battery/charging system warning light on the dashboard. Keeping the battery case clean by wiping it down with a moist paper towel and mild detergent will help reduce any current drain caused by dirt or grime. Batteries loose 30 percent of their power at temperatures around freezing and over 60 percent when temperatures drop to zero degrees.

Corrosion around the terminal connections and battery hold down can be cleaned with a small stiff brush and a solution of baking soda and water. Rinse the battery with water, but be careful not to stain floors or driveways.

If the battery has removable vent caps, check the electrolyte fluid level. It should be above the tops of the plates inside the battery. If fluid is needed add distilled water, but do not overfill.

Battery terminal connections should be tight. Adjust loose fittings or replace fittings that have cracked. When working around automotive batteries always wear proper eye protection, gloves and never smoke or work near an open flame. Explosive hydrogen gas is present and may explode.

Instructions for jump starting a failed battery can be found in vehicle owners’ manuals, however, jump-starting can be dangerous and motorists that are uncertain about battery maintenance and safety should seek professional assistance from a certified technician or a qualified emergency road service provider.

When selecting a new battery, always choose one that is of the same physical size as the original battery. This will ensure proper fit and avoid excessive vibration, which will shorten battery life.

Never install a battery with a lower than the vehicle manufacturer’s recommended rating.